A typical separable connector comprises a first module that is movable through an operating stroke and a stationary second module that is adapted to couple with the first module. The movable module typically takes the form of an elbow that comprises: (i) a conductive connector member that is connected by a crimp joint to an incoming cable and (ii) a contact rod that is joined to the connector member through a threaded joint. Typically, this threaded joint comprises external threads on one end of the contact rod and internal threads in a hole in the connector member that are adapted to mate with the external threads of the contact rod. This threaded joint serves to mechanically and electrically interconnect the connector member and the contact rod. Force applied to the connector member is used for driving the contact rod into and out of engagement with mating contacts in the stationary module. When the mating contacts are engaged or are being operated into or out of engagement, current flows through the threaded joint, developing thermal and magnetic conditions therein that must be successfully withstood without deterioration of the joint. Also, the mechanical stresses developed by connector operation must be sucessfully withstood without deterioration of the joint. A low resistance connection must be maintained at this threaded joint to avoid overheating.
Maintaining a low resistance connection at this joint has proven to be a difficult problem. One approach to overcoming this problem has been to use one or more spring washers between the contact rod and connector to maintain axial tension on the threads of the contact rod. Because of space limitations these washers cannot be very large, and the washers that have been used have been found not very effective in preventing the threads from eventually loosening as a result of vibrations or of strains produced by operating forces.
Another approach that has been considered is to use thread-locking techniques that involve distortion of the mating metallic threads prior to assembly. A disadvantage of this approach is that a typical amount of thread distortion produces an excessively wide range of assembly torques. Low assembly torque would be associated with insufficient thread locking. High assembly torque would likely result in the incomplete installation of the contact rod. Variations in material and dimensions can significantly affect the amount of torque that is appropriate.
Still another approach that we have considered is to use a plastic insert around the full circumference of the internally threaded member. This seems to be not as effective as might be desired because the plastic insert tends to keep the externally threaded contact rod centered, thus inhibiting good high pressure engagement between the mating threads.